Contents

The HK417 is similar in internal design to the HK416, although the receiver and working parts are enlarged to suit the larger 7.62×51mm cartridge. The bolt is a seven-lug rotating type, which sits in a bolt carrier and operates in a forged alloy receiver resembling those of the Stoner-designed AR-10, AR-15 and M16 rifles.

The early HK417 prototype used 20-round magazines from the Heckler & Koch G3 rifle family, which did not feature a bolt hold-open device. Later prototypes, however, switched to a polymer magazine with bolt hold-open. The magazine resembles an enlarged version of the G36's transparent magazine, except without the pins for holding more than one magazine together.

Purchasers of the HK417 have typically intended it to complement lighter assault rifles chambered for less powerful intermediate cartridges (often 5.56×45mm NATO), for the designated marksman role. The HK417's greater accuracy, effective range, and penetration offset its greater expense, its lower rate of fire, and its smaller ammunition capacity both in magazine and carriage.[2]

The HK417 A2 is the improved version. The design of the receiver, barrel interface, gas port and the bore axis alignment of the rifle have been further optimised to increase its accuracy and reliability.[2][3] The German Army uses the HK417 A2 - 13″ with the designation G27.[2][4]

As of 2013, the HK417 A2 models chambered for 7.62×51mm NATO available to the military and law enforcement market are:

HK417 A2 - 13″: carbine with 330.2 mm (13 in) barrel

HK417 A2 - 16.5″: rifle with 419.1 mm (16.5 in) barrel

HK417 A2 - 20″: "full size" rifle with 508.0 mm (20 in) barrel

Accurized barrels provide 0.3 mil (1 moa) accuracy (with match grade ammunition). A barrel can be changed in under two minutes with simple tools. All HK417 barrels are cold hammer forged and chrome-lined and use a conventional lands and grooves bore profile with a twist rate of 1 turn in 279.4 mm (11.00 in). They are designed to function reliably with bullet weights ranging from 9.3 to 11.34 g (144 to 175 gr) and are threaded for a flash hider or sound suppressor.[2][5]

The civilian MR308 was used to develop the G28, a designated marksman rifle for the German Bundeswehr (Federal Army) deployment to the War in Afghanistan. The semi-automatic G28 is chambered for 7.62×51mm NATO and has a factory warrantied accuracy of 45 mm dispersion at 100 meters (0.45 mil or 1.5 moa) when fired with 10 rounds using OTM/HPBT/Sierra Match King ammunition. The G28 features STANAG 4694 NATO Accessory Rails that are backwards-compatible with the STANAG 2324/MIL-STD-1913 Picatinny rails. The upper receiver is made from steel instead of HK's aluminium alloy. Approximately 75% of the parts are interchangeable with the HK417. There are two different versions of the G28: G28 E2 (Standard) with a Schmidt & Bender 3–20×50 PM II (modified to Bundeswehr requirements) and the G28 E3 (Patrol) with Schmidt & Bender 1–8×24 PM II.[6] By October 2017, Heckler & Koch had renamed the G28 as the HK241, though G28 remains its Bundeswehr designation.[7]

In March 2018, the Army announced that a version of the G28/M110A1 would be issued to infantry squads as the service's standard Squad Designated Marksman Rifle (SDMR). Issuing a 7.62 mm SDMR is meant to increase individual squads' ability to defeat enemy body armor that standard 5.56 mm rounds cannot penetrate.[12] The M110A1-based rifle will replace the M14 EBR, in use by the Army since 2009, but because it was based on an operational needs statement it had to be turned in by units at the end of a combat deployment. Unlike the sniper configuration, the marksman version is fitted with a simpler rifle optic instead of a telescopic sight to make quick adjustments between 0-600 meters, and it fires M80A1 Enhanced Performance Rounds rather than sniper rounds; it will be fielded with a suppressor to make the marksman less identifiable with louder 7.62 mm rounds. Roughly 6,000 are planned to be fielded with one per squad in infantry, engineer and scout formations starting in late 2018.[13]

The MR308 is a civilian variant of the HK417, introduced in 2007 alongside the MR223, a civilian HK416.[14] It is a semi-automatic rifle with several "sporterized" features. At the 2009 SHOT Show, the two rifles were introduced to the American civilian market as the MR762 and MR556, respectively.[15] Since then both were replaced by the improved MR762A1 and MR556A1.[16][17]

1.
Gun barrel
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A gun barrel is a part of firearms and artillery pieces. The hollow interior of the barrel is called the bore, a gun barrel must be able to hold in the expanding gas produced by the propellants to ensure that optimum muzzle velocity is attained by the projectile as it is being pushed out by the expanding gas. Modern small arms barrels are made of known and tested to withstand the pressures involved. Artillery pieces are made by various techniques providing reliably sufficient strength, early firearms were muzzle-loading, with powder, and then shot loaded from the muzzle, capable of only a low rate of fire. During the 19th century effective mechanical locks were invented that sealed a breech-loading weapon against the escape of propellant gases, the early Chinese, the inventors of gunpowder, used bamboo, a naturally tubular stalk, as the first barrels in gunpowder projectile weapons. Early European guns were made of iron, usually with several strengthening bands of the metal wrapped around circular wrought iron rings. The Chinese were the first to master cast-iron cannon barrels, early cannon barrels were very thick for their caliber. Bore evacuator Bore snake Cannon Muzzle Polygonal rifling Rifling Slug barrel Smoothbore

2.
Action (firearms)
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In firearms terminology, an action is the mechanism that handles the ammunition or the method by which that mechanism works. Breech-loading weapons have actions, actions are not present on muzzleloaders. The mechanism that fires a muzzle-loader is called the lock, actions can be categorized in several ways, including single action versus double action, break action versus bolt action, and others. The term action can also short, long, and magnum if it is in reference to the length of the rifle’s receiver. The short action rifle usually can accommodate a cartridge length of 2.8 in or smaller, the long action rifle can accommodate a cartridge of 3.34 in, and the magnum action rifle can accommodate cartridges of 3.6 in, or longer in length. Manual operation is a term describing any type of firearm action that is loaded one shot at a time by the user rather than automatically. For example, break action is a form of operation using a simple hinge mechanism that is manually unlatched by the operator. These are actions wherein the breechblock lowers or drops into the receiver to open the breech, there are two principal types of dropping block, the tilting block and the falling block. In a tilting or pivoting block action, the breechblock is hinged on a pin mounted at the rear, when the lever is operated, the block tilts down and forward, exposing the chamber. The best-known pivoting block designs are the Peabody, the Peabody–Martini, the original Peabody rifles, manufactured by the Providence Tool Company, used a manually cocked side-hammer. The 1871 Martini–Henry which replaced the trapdoor Snider–Enfield was the standard British Army rifle of the later Victorian era, charles H. Ballards self-cocking tilting-block action was produced by the Marlin Firearms Company from 1875, and earned a superlative reputation among long-range Creedmoor target shooters. Surviving Marlin Ballards are today highly prized by collectors, especially those mounted in the elaborate Swiss-style Schützen stocks of the day. A falling-block action is a firearm action in which a solid metal breechblock slides vertically in grooves cut into the breech of the weapon. Examples of firearms using the falling block action are the Sharps rifle, in a rolling block action the breechblock takes the form of a part-cylinder, with a pivot pin through its axis. The operator rotates or rolls the block to open and close the breech, it is a simple, rugged, a break action is a type of firearm where the barrel are hinged and can be broken open to expose the breech. The earliest metallic-cartridge breechloaders designed for military issue began as conversions of muzzle-loading rifle-muskets. The upper rear portion of the barrel was filed or milled away, an internal angled firing pin allowed the re-use of the rifles existing side-hammer. The Allin action made by Springfield Arsenal in the US hinged forward, france countered in 1866 with its superior Chassepot rifle, also a paper-cartridge bolt action

3.
Magazine (firearms)
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A magazine is an ammunition storage and feeding device within or attached to a repeating firearm. Magazines can be removable or integral to the firearm, the magazine functions by moving the cartridges stored in the magazine into a position where they may be loaded into the chamber by the action of the firearm. The detachable magazine is often referred to as a clip, although this is technically inaccurate, magazines come in many shapes and sizes, from those of bolt-action express rifles that hold only a few rounds to drum magazines for self-loading rifles that can hold one hundred rounds or more. Various jurisdictions ban what they define as high-capacity magazines, with the increased use of semi-automatic and automatic firearms, the detachable box magazine became increasingly common. Soon after the adoption of the M1911 pistol, the magazine was settled on by the military and firearms experts. The defining difference between clips and magazines is the presence of a mechanism in a magazine, typically a spring-loaded follower. Use of the clip to refer to detachable magazines is a point of strong disagreement. The first mass-produced repeater was the Volcanic Rifle which used a bullet with the base filled with powder and primer fed into the chamber from a spring-loaded tube called a magazine. It was named after a building or room used to store ammunition, the anemic power of the Rocket Ball ammunition used in the Volcanic doomed it to limited popularity. The Henry repeating rifle is a lever-action, breech-loading, tubular magazine fed rifle, designed by Benjamin Tyler Henry in 1860, it was one of the first firearms to use self-contained metallic cartridges. The Henry was introduced in the early 1860s and produced through 1866 in the United States by the New Haven Arms Company and it was adopted in small quantities by the Union in the Civil War and favored for its greater firepower than the standard issue carbine. Many later found their way West and was famed both for its use at the Battle of the Little Bighorn, and being the basis for the iconic Winchester rifle which are made to this day. The Henry and Winchester rifles would go on to see service with a number of militaries including Turkey, switzerland and Italy adopted similar designs. The first magazine-fed firearm to achieve success was the Spencer repeating rifle. The Spencer used a magazine located in the butt of the gun instead of under the barrel. The Spencer was successful, but the rimfire ammunition did occasionally ignite in the magazine tube and it could also injure the user. The new bolt-action rifles began to favor with militaries in the 1880s and were often equipped with tubular magazines. The Mauser Model 1871 was originally a single-shot action that added a magazine in its 1884 update

4.
Iron sights
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Iron sights are typically composed of two component sights, formed by metal blades, a rear sight mounted perpendicular to the line of sight and a front sight that is a post, bead, or ring. Open sights use a notch of some sort as the rear sight, civilian, hunting, and police firearms usually feature open sights, while many military battle rifles employ aperture sights. The earliest and simplest iron sights are fixed and cannot be easily adjusted, many iron sights are designed to be adjustable, so that the sights can be adjusted for elevation or windage. On many firearms it is the sight that is adjustable. For precision applications such as hunting or sniping, the sights are usually replaced by a telescopic sight. Iron sights may still be fitted alongside other sighting devices for back-up usage, iron sights provide horizontal and vertical reference points that allow the shooter to train the weapon. Rear sights are mounted in a dovetail on the barrel or receiver, closer to the eye of the shooter. Front sights are mounted to the barrel by dovetailing, soldering, screwing, or staking close to the muzzle, frequently on a ramp. Some front sight assemblies include a detachable hood intended to reduce glare, with typical blade or post iron sights, the shooter would center the front post in the notch of the rear sight and the tops of both sights should be level. Since the eye is capable of focusing on one plane, and the rear sight, front sight. At 1,000 m, that same misalignment would be magnified 100 times, sights for shotguns used for shooting small, moving targets work quite differently. The rear sight is completely discarded, and the reference point is provided by the correct. A brightly colored round bead is placed at the end of the barrel, often, this bead will be placed along a raised, flat rib, which is usually ventilated to keep it cool and reduce mirage effects from a hot barrel. This method of aiming is not as precise as that of a front sight/rear sight combination, but it is faster. Some shotguns also provide a mid-bead, which is a smaller bead located halfway down the rib, open sights generally are used where the rear sight is at significant distance from the shooters eye. They provide minimum occlusion of the view, but at the expense of precision. Open sights generally use either a square post or a bead on a post for a front sight, to use the sight, the post or bead is positioned both vertically and horizontally in the center of the rear sight notch. For a center hold, the front sight is positioned on the center of the target, for a 6oclock hold, the front sight is positioned just below the target and centered horizontally

5.
Heckler & Koch HK416
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The Heckler & Koch HK416 is an assault rifle/carbine designed and manufactured by Heckler & Koch. The United States Armys Delta Force, at the request of R&D NCO Larry Vickers, the project was originally called the Heckler & Koch M4, but this was changed in response to a trademark infringement suit filed by Colt Defense. Delta Force replaced its M4s with the HK416 in 2004, after tests revealed that the operating system significantly reduces malfunctions while increasing the life of parts. The HK416 has been tested by the United States military and is in use with some law enforcement agencies and it has also been adopted as the standard rifle of the Norwegian Armed Forces and the French Armed Forces. A modified variant underwent testing by the United States Marine Corps as the M27 Infantry Automatic Rifle, after the Marine Corps Operational Test & Evaluation Activity supervised a round of testing at MCAGCC Twentynine Palms, Fort McCoy, and Camp Shelby. As of March 2012, fielding of 452 IARs has been completed of 4,748 ordered, the HK416 uses a HK-proprietary short-stroke gas system that derives from the HK G36, forgoing the expanding gas system standard in AR-15 rifles. The HK G36 gas system was in turn derived from the AR-18 assault rifle designed in 1963. The HK system uses a short-stroke piston driving a rod to force the bolt carrier to the rear. This design prevents combustion gases from entering the weapons interior—a shortcoming with direct impingement systems, the reduction in heat and fouling of the bolt carrier group increases the reliability of the weapon and extends the interval between stoppages. During factory tests the HK416 fired 10,000 rounds in full-auto without malfunctioning and it also reduces operator cleaning time and stress on critical components. According to H&K, experience that Heckler & Koch gained during its highly successful midlife improvement programme for the British Army SA80 assault rifle, have now borne fruit in the HK416, the HK416 is equipped with a proprietary accessory rail forearm with MIL-STD-1913 rails on all four sides. This lets most current accessories for M4/M16-type weapons fit the HK416, the HK416 rail forearm can be installed and removed without tools by using the bolt locking lug as the screwdriver. The rail forearm is free-floating and does not contact the barrel, the HK416 has an adjustable multi-position telescopic butt stock, offering six different lengths of pull. The shoulder pad can be convex or concave and the stock features a storage space for maintenance accessories. The trigger pull is 34 N, the empty weight of a HK416 box magazine is 250 g. The HK416s barrel is cold hammer-forged with a 20, 000-round service life, the cold hammer-forging process provides a stronger barrel for greater safety in case of an obstructed bore or for extended firing sessions. Modifications for an over-the-beach capability such as holes in the bolt carrier and buffer system are available to let the HK416 fire safely after being submerged in water. The HK416s outer appearance resembles the M4 and it includes international symbols for safe, semi-automatic, and fully automatic

6.
Military
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The armed forces of a country are its government-sponsored defense, fighting forces, and organizations. They exist to further the foreign and domestic policies of their body and to defend that body. Armed force is the use of armed forces to achieve political objectives, the study of the use of armed forces is called military science. Broadly speaking, this involves considering offense and defense at three levels, strategy, operational art, and tactics, all three levels study the application of the use of force in order to achieve a desired objective. In most countries the basis of the forces is the military. However, armed forces can include other paramilitary structures, the obvious benefit to a country in maintaining armed forces is in providing protection from foreign threats and from internal conflict. In recent decades armed forces personnel have also used as emergency civil support roles in post-disaster situations. On the other hand, they may harm a society by engaging in counter-productive warfare. Expenditure on science and technology to develop weapons and systems sometimes produces side benefits, although some claim that greater benefits could come from targeting the money directly

7.
Special forces
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Special forces and special operations forces are military or police units trained to conduct special operations. The term special forces in the United States refers to the U. S. Armys forces, in Russian-speaking countries special forces are typically called spetsnaz, an acronym for special purpose. Likewise, Russian speakers refer to special forces of nations as spetsnaz, for example. Special Forces would be referred to as amerikanski spetsnaz in Russian, other significant roles lay in reconnaissance, providing essential intelligence from near or among the enemy and increasingly in combating irregular forces, their infrastructure and activities. Hamilcar Barca in Sicily had specialized troops trained to launch several offensives per day, in the late Roman or early Byzantine period, Roman fleets used small, fast, camouflaged ships crewed by selected men for scouting and commando missions. In Japan, ninjas were used for reconnaissance, espionage and as assassins, bodyguards or fortress guards, during the Napoleonic wars, rifle and sapper units were formed that held specialised roles in reconnaissance and skirmishing and were not committed to the formal battle lines. The British Indian Army deployed two special forces during their wars, the Corps of Guides formed in 1846 and the Gurkha Scouts. During the Second Boer War the British Army felt the need for specialised units became most apparent. This unit was formed in 1900 by Lord Lovat and early on reported to an American, Major Frederick Russell Burnham, after the war, Lovats Scouts went on to formally become the British Armys first sniper unit. Additionally, the Bushveldt Carbineers, formed in 1901, can be seen as an unconventional warfare unit. Modern special forces emerged during the Second World War, in 1940, the British Commandos were formed following Winston Churchills call for specially trained troops of the hunter class, who can develop a reign of terror down the enemy coast. A staff officer, Lieutenant Colonel Dudley Clarke, had already submitted such a proposal to General Sir John Dill, Dill, aware of Churchills intentions, approved Clarkes proposal and on 23 June 1940, the first Commando raid took place. The Special Service Brigade was quickly expanded to 12 units which became known as Commandos, each Commando had a lieutenant colonel as the commanding officer and numbered around 450 men. In December 1940 a Middle East Commando depot was formed with the responsibility of training and supplying reinforcements for the Commando units in that theatre, in February 1942 the Commando training depot at Achnacarry in the Scottish Highlands was established by Brigadier Charles Haydon. Under the command of Lieutenant Colonel Charles Vaughan, the Commando depot was responsible for training complete units, the training regime was for the time innovative and physically demanding, and far in advance of normal British Army training. The depot staff were all hand picked, with the ability to any of the volunteers. Training and assessment started immediately on arrival, with the volunteers having to complete an 8-mile march with all their equipment from the Spean Bridge railway station to the commando depot, exercises were conducted using live ammunition and explosives to make training as realistic as possible. Physical fitness was a prerequisite, with cross country runs and boxing matches to improve fitness, speed and endurance marches were conducted up and down the nearby mountain ranges and over assault courses that included a zip-line over Loch Arkaig, all while carrying arms and full equipment

8.
Police
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A police force is a constituted body of persons empowered by the state to enforce the law, protect property, and limit civil disorder. Their powers include the use of force. Law enforcement, however, constitutes part of policing activity. Policing has included an array of activities in different situations, in some societies, in the late 18th and early 19th centuries, these developed within the context of maintaining the class system and the protection of private property. Many police forces suffer from police corruption to a greater or lesser degree, the police force is usually a public sector service, meaning they are paid through taxes. Alternative names for police force include constabulary, gendarmerie, police department, police service, crime prevention, protective services, law enforcement agency, members may be referred to as police officers, troopers, sheriffs, constables, rangers, peace officers or civic/civil guards. As police are often interacting with individuals, slang terms are numerous, many slang terms for police officers are decades or centuries old with lost etymology. One of the oldest, cop, has largely lost its slang connotations and this is derived from πόλις, city. Law enforcement in ancient China was carried out by prefects for thousands of years since it developed in both the Chu and Jin kingdoms of the Spring and Autumn period, in Jin, dozens of prefects were spread across the state, each having limited authority and employment period. Under each prefect were subprefects who helped collectively with law enforcement in the area, some prefects were responsible for handling investigations, much like modern police detectives. The concept of the system spread to other cultures such as Korea. In ancient Greece, publicly owned slaves were used by magistrates as police, in Athens, a group of 300 Scythian slaves was used to guard public meetings to keep order and for crowd control, and also assisted with dealing with criminals, handling prisoners, and making arrests. Other duties associated with modern policing, such as investigating crimes, were left to the citizens themselves, in the Roman empire, the army, rather than a dedicated police organization, provided security. Local watchmen were hired by cities to some extra security. Magistrates such as fiscal and quaestors investigated crimes. There was no concept of public prosecution, so victims of crime or their families had to organize and their duties included apprehending thieves and robbers and capturing runaway slaves. The vigiles were supported by the Urban Cohorts who acted as a heavy-duty anti-riot force, in medieval Spain, Santa Hermandades, or holy brotherhoods, peacekeeping associations of armed individuals, were a characteristic of municipal life, especially in Castile. These organizations were intended to be temporary, but became a fixture of Spain

9.
ArmaLite AR-10
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The AR-10 is a 7. 62×51mm NATO battle rifle developed by Eugene Stoner in the late 1950s at ArmaLite, then a division of the Fairchild Aircraft Corporation. Over its production life, the original AR-10 was built in small numbers. In 1957, the basic AR-10 design was rescaled and substantially modified by ArmaLite to accommodate the.223 Remington cartridge, ArmaLite licensed the AR-10 and AR-15 designs to Colt Firearms. The AR-15 eventually became the M16 rifle, ArmaLite began as a small engineering concern founded by George Sullivan, the patent counsel for Lockheed Corporation, and funded by Fairchild Engine and Airplane Corporation. On October 1,1954, the company was incorporated as the ArmaLite Corporation, with its limited capital and tiny machine shop, ArmaLite was never intended to be an arms manufacturer. The company focused on producing small arms concepts and designs to be sold or licensed to other manufacturers, at the time, ArmaLite Inc. was a very small organization. With Stoner as chief engineer, ArmaLite quickly released a number of interesting rifle concepts. The first prototypes of the 7.62 mm AR-10 emerged during 1955, at the time the United States Army was in the midst of testing several rifles to replace the obsolete M1 Garand. Springfield Armorys T44E4 and heavier T44E5 were essentially updated versions of the Garand chambered for the new 7.62 mm round, the AR-10 prototypes featured a straight-line stock design, rugged elevated sights, an oversized aluminum flash suppressor and recoil compensator, and an adjustable gas system. For a 7. 62mm NATO rifle, the AR-10 prototype was incredibly lightweight at only 6.85 lbs. empty, initial comments by Springfield Armory test staff were favorable, and some testers commented that the AR-10 was the best lightweight automatic rifle ever tested by the Armory. Unfortunately for ArmaLite, the rifles aluminum/steel composite barrel burst in a torture test conducted by Springfield Armory in early 1957, ArmaLite quickly replaced it with a conventional steel barrel, but the damage had been done. The final Springfield Armory report advised against adoption of the rifle, Army infantry forces urgently required a modern, magazine-fed infantry rifle to replace the M1. In the end the Army chose the conventional T44, which entered production as the M14 rifle in 1957. That same year, ArmaLite completed about 50 production AR-10 rifles at its workshop for use as models for its sales agents, including Samuel Cummings. Attempts to rush completion of fifty rifles resulted in a few units that were assembled with improperly machined barrel extensions. These production rifles built at ArmaLites workshop in Hollywood would later become known as the Hollywood model, on July 4,1957, Fairchild ArmaLite sold a five-year manufacturing license for the AR-10 to the Dutch arms manufacturer, Artillerie Inrichtingen. With its large factory and production facilities, A. I. could produce the ArmaLite rifle in the quantities for which Fairchild expected orders would be forthcoming. In 1957 Cummings secured an order of 7,500 AR-10 rifles from Nicaragua, the order was contingent on a successful completion of a 7, 500-round endurance test

A telescopic sight, commonly called a scope, is an optical sighting device that is based on a refracting telescope. …

View through a 4x rifle scope.

Telescopic sight (German made ZF Ajack 4×90 (4×38 in modern terminology)) for the World War II pattern Swedish sniper rifle m/1941.

A Swift model 687M variable power rifle scope with parallax compensation (the ring around the objective lens is used for making parallax adjustments).

A typical (stadiametric) rangefinding reticle used by military snipers. The Mil-dots can be seen on the cross hairs. The four horizontal bars over the horizontal line are also intended for (quick) ranging purposes.

A cartridge is a type of firearm ammunition packaging a projectile (bullet, shots or slug), a propellant substance …

A modern cartridge consists of the following: 1. the bullet, as the projectile; 2. the case, which holds all parts together; 3. the propellant, for example gunpowder or cordite; 4. the rim, which provides the extractor on the firearm a place to grip the casing to remove it from the chamber once fired; 5. the primer, which ignites the propellant.